JPH0348020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a heat-shrinkable tube.

(Prior art) Examples of means for continuously manufacturing heat-shrinkable tubes include US Pat. No. 3,370,112 and Japanese Patent Publication No. 38-26581
No. and Special Publication No. 55-6045 are known.

First, the method shown in US Pat. No. 3,370,112 involves heating an internally pressurized crystalline polymer resin tube in a heating bath to a temperature above the crystal melting point, passing it through a sealing die in the heated state, and drawing it into a decompression chamber. This is a method of obtaining a heat-shrinkable tube by introducing the tube into a molded tube equipped with a cooling device while expanding the diameter by the differential pressure between them, and cooling and fixing the tube.

(Problem to be Solved by the Invention) The biggest problem when expanding the diameter of a tube using such a differential pressure is the method of maintaining the reduced pressure. The contact area between the two changes, and the friction between the two changes, and the elongation in the length direction due to the pulling force of the enlarged diameter tube changes, and as a result, it is often impossible to obtain a product that is uniform and has a small amount of elongation.

Japanese Patent Publication No. 38-26581 proposes a method of suppressing the longitudinal elongation of the tube as much as possible by using, for example, an endless belt engaged with a slide fastener as a conveyance means. However, other drawbacks have been pointed out in this method, such as the use of the endless belt reduces cooling efficiency and complicates the apparatus.

In addition, the method disclosed in Japanese Patent Publication No. 55-6045 uses an expansion control cooling tube having through holes in the tube wall based on the idea of solving the above problem by performing the tube diameter expansion and cooling in a series. This method expands the diameter of the tube. However, in this case, the heating medium adhering as a lubricant to the surface of the heat-shrinkable tube whose diameter has been expanded to the inner diameter of the expansion control cooling tube is pushed out through the tube wall through-hole, and as a result, the heating medium is forced out through the tube wall through-hole. Increases the frictional resistance between the wall and the expanded tube. Moreover, there is a problem that the tube may sink into the through hole, which may encourage an increase in frictional resistance. This problem is particularly serious when a tube with a thin wall is used or when the diameter expansion magnification is large.

The inventors previously proposed a method in which the outside pressure of the tube is divided into two decompression chambers in the direction of movement of the tube and performed separately to provide a differential pressure when expanding the tube diameter. Great results were achieved by successfully suppressing the tube's longitudinal elongation and achieving stable diameter expansion.

However, in each of the above methods, the introduction part of the tube into the enlarged diameter part is sealed by, for example, partial contact between a sealing die and the outside of the tube, and the air pressure is reduced due to changes in the clearance of the seal part due to changes in the tube diameter. The amount of suction into the chamber changes, and this change is especially large on the tube intake side, and the degree of vacuum in the decompression chamber becomes unstable, which destabilizes the amount of tube expansion and prevents uniformity of product quality. Ta.

In order to stabilize the degree of vacuum mentioned above, it is necessary to install a large-capacity vacuum pump, but on the other hand, this has an unavoidable cost disadvantage.

(Means for Solving the Problems) As a result of intensive studies to solve these problems, the inventors installed a tube with a diameter slightly larger than the outside diameter of the unexpanded tube at the end on the introduction side of the tube into the decompression chamber. By installing a cylindrical body, supplying heated liquid to the tube introduction part through this cylindrical body, and sealing the introduction side of the casing to stabilize the degree of vacuum in the casing while expanding the diameter of the tube. discovered that the above degree of vacuum could be stabilized and completed this invention.

That is, this invention consists of a case in which a thermoplastic tube under heating and softening is sealed from one side with an unexpanded diameter tube on the introduction side and an expanded diameter tube on the withdrawal side, and is equipped with appropriate pressure reducing means,
The tube is introduced into the enlarged diameter part of the tube, which constitutes a cooling sing part in which the outer periphery of the enlarged tube is inscribed and cooled. In the method for manufacturing a heat-shrinkable tube, the diameter of the tube is enlarged, the diameter is cooled and fixed in the cooling sizing part, and the tube is pulled to the other side, and the tube introduction side end of the casing is equipped with the pressure reducing means. A cylindrical body with a diameter slightly larger than the outside diameter of the unexpanded tube is installed in the cylindrical body, and the heated liquid is supplied to the tube introduction part through this cylindrical body, and the inlet side of the casing is sealed. This is a method for manufacturing a heat-shrinkable tube, characterized in that the diameter of the tube is expanded while the degree of pressure reduction is stabilized.

(Function) In the present invention, on the tube introduction side, the unexpanded diameter tube is introduced in substantially contact with the inside of the cylindrical body of the desired length, and the heated liquid is always present in the gap between them. As a result, even if the outer diameter of the tube changes slightly, no air is taken into the decompression chamber, and a stable degree of vacuum can be maintained even with the capacity of a small vacuum pump.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall explanatory diagram of the method for continuously expanding the diameter of a heat-shrinkable tube of the present invention, and 1 is an unexpanded tube 1.
3a is a winding reel for feeding;
The tube 13a is pressurized inside and sent into the heating tank 4 via the guide rolls 2 and 3. The heating tank 4 is filled with a liquid heating medium, and while the tube 13a passes between the guide rolls 5 and 6, it is heated and softened, and at the same time, the tube 13a is slightly expanded in diameter in response to the internal pressurization.

The heating liquid heat medium mentioned above is most commonly silicone oil or glycerin, but other liquids can be used as long as they are fluid at room temperature. It is desirable for this to have as low a viscosity as possible upon cooling.

The preheated unexpanded tube 13a is guided by guide rolls 7 and introduced into the expanded diameter section 10 via a cylindrical body 8 having a slightly larger diameter. This enlarged diameter portion 10 is shown enlarged in FIG. Reference numeral 11 denotes, for example, a horizontal cylindrical case with a decompression chamber 11a inside, and an unexpanded diameter tube 1.
On the introduction side of 3a, there is a sealing die 12 having an introduction hole 12a approximately equal to the outer diameter of the unexpanded tube 13a.
is attached, and the above-mentioned cylindrical body 8 of approximately the same or slightly larger diameter is installed extending to the introduction side, and a heating medium supply pipe 8a is installed at a desired intermediate position of the cylindrical body 8.
Connect and leave opening 8b.

Inside the case 11, there is a tube 13 with an enlarged diameter in the axial direction.
A cooling sizing portion 14 corresponding to the diameter of the cooling sizing portion 14 is provided in the axial direction in a conventional manner.

A decompression means 18 is connected to the decompression chamber 11a, as shown in FIG. 2, which includes a vacuum trap 15, a vacuum gauge 16, and a vacuum pump 17 arranged in this order.
In the expanded diameter section 10 having such a configuration, the unexpanded diameter tube 13a described above is introduced into the introduction hole 12a through the cylindrical body 8, guided so that it is successively taken up through the introduction hole 12a, and is successively taken up through this into a take-up section to be described later. The pressure reducing means 18 is operated.

The unexpanded diameter tube 13a is expanded in diameter as shown in the figure, cooled while being inscribed in the cooling sizing part 14, and taken as the expanded diameter tube 13.

At this time, the heating medium attached to the unexpanded tube in the heating tank 4 and the same heating medium supplied through the supply pipe 8a satisfy the clearance between the unexpanded tube 13a and the cylindrical body 8, and tube 1
It is possible to eliminate the intake of air into the decompression chamber side due to fluctuations in the outer diameter of 3a, and to maintain the degree of vacuum stably. Also, since the remaining heating medium is present at this time, it constantly moves with the movement of the tube and functions as a lubricant.

The enlarged diameter tube 13, which has been enlarged in diameter and cooled and fixed as described above, is guided to the cooling bath 19 shown in FIG. and is pulled and wound onto the take-up reel 21. In this case, it is preferable to provide an air blower (not shown) either before or after the take-up roll 20 to remove the cooling water adhering to the cooling tank.

Next, FIG. 3 shows another embodiment of the present invention. FIG. 3 shows the unexpanded diameter tube 13 of the aforementioned expanded diameter section 10.
The cylindrical body 8 provided at the inlet of the heating tank 4 is directly connected to the outlet side of the heating tank 4, and the separate heating medium supply pipe 8 is connected directly to the outlet side of the heating tank 4.
This is an example in which a is omitted.

According to this example, the adhering heating medium in the direct heating tank 4 is applied to the cylindrical body 8 and the unexpanded tube 13 in a necessary and sufficient amount.
It is supplied to the clearance between spaces a and contributes to the above-mentioned stabilization of the degree of vacuum.

In FIG. 3, the same parts are given the same reference numerals, and other explanations are omitted.

(Effects of the Invention) As explained above, according to the present invention, when manufacturing a heat-shrinkable tube, the unexpanded diameter tube is brought into approximate contact with the inner side of a cylindrical body having a desired length on the tube introduction side of the tube expansion section. Since heated liquid is introduced and always exists in the gap between them, even if the outer diameter of the tube changes slightly, there is no air intake into the decompression chamber, and the degree of vacuum is stable according to the capacity of the vacuum pump. is maintained, and therefore it is possible to stably obtain a heat-shrinkable tube that is homogeneous and has sufficient shrinkage characteristics with good workability without installing a large-capacity vacuum pump.

[Brief explanation of drawings]

FIG. 1 is an enlarged view of the essential parts of an example apparatus for carrying out the method of the present invention, FIG. 2 is a schematic diagram of the entire same, and FIG. 3 is an enlarged view of the essential parts of another embodiment. DESCRIPTION OF SYMBOLS 1... Feeding reel, 4... Heating tank, 8... Cylindrical body, 8a... Heating medium supply pipe, 10... Expanded diameter part, 14
...cooling sizing section, 13, 13a...tube,
19... Cooling tank, 21... Winding section.

Claims (1)

[Claims] 1 From one side, a thermoplastic tube under heating and softening is sealed with an unexpanded tube on the introduction side and an expanded diameter tube on the take-off side, and the tube is expanded in diameter. The tube is introduced into the expanded diameter part of the tube, which constitutes a cooling sizing part where the outer periphery of the tube is internally cooled. In the method for manufacturing a heat-shrinkable tube, in which the diameter is expanded, the diameter is cooled and fixed in the cooling sizing section, and the tube is pulled to the other side, the tube introduction side end of the casing equipped with the pressure reducing means has an unexpanded diameter. A cylindrical body with a diameter slightly larger than the outside diameter of the tube is installed, and the heated liquid is supplied to the tube introduction part through this cylindrical body, and the inlet side of the casing is sealed to stabilize the degree of vacuum in the casing. A method for manufacturing a heat-shrinkable tube, characterized in that the tube diameter is expanded at the same time.